Communication system



sep 9 vF. B. MONAR 1,324,784

COMMUNI CATION SYSTEM Filed May '15, 1928 IN V EN TOR.

BY qw d vvfi'.

ATTORNEYS.

Patented Sept. 29, 1931 UNITED STA-TIE FRED Jimmie: or wasnine'ron'nrsrnicror coLnMnrA commomcA'rron sysrnmf Applicationvflled nay 15, 1928. Serial 1151217339;

(GRANTED timer, m c: or imncna js as; As mnnnn maniac, 1928; 37d 0. 6. 757

- My invention 1 relates ibroadly to'communi cation systems and more particularly t o a system of intercommunication "between 'a plurality of stations, for example, between: the difiere'nt members of the-crewof an 3 11" craft. t I

The object of my invention is to provide a reliable system of intercommunication,

c which will retain its reliability'in'spite of external noises ofgreat volume. n

A further object of my inventionis to provide an intercommunica'tion system which is an integral part of the radio receiving sysir tem of an aircraft, thus doing away with the necessity for the extra batteries,- trans'fo'rmi ers' and switching devices required whenf a separate interconmiuiilcation system 1s "em ployed as heretofore. The savmg-of weight thus accomplished is; of itself, 'a great advantage over the intercommunication'systems heretofore used. 1 Y 7 i Further objects of my invention'will appear more fully'hereinafter as the descrip-' tion of veloped. V t

My invention consists substantially in the :onstruction, combination and arrangement of parts associated therewith or aswill be i more fully hereinafter set forth as shown by the accompanyingdrawing 9 and finally pointed out in the appended claims. r

i The drawing forming a part of thisspecification represents a circuit embodyingmy invention. The vacuum tube 1 is 'of'the ordinary three electrode type, which maybe one of the tubes of the radio receiving set of an aircraft; that is, ifan aircraft has 'a radio receiving set, one of the tubes :of'said. set

may be associated withthe circuit of-my-invention without interferingiwith the normal function of said tube in said receiving set; For purposes of this description I have shownthe tube as the detector tube of a receiving set connected as an oscillator ofthe" autodyne type, as in thismanneroral'intercommunication may with special easebe reiiably-efiected as hereafter described. Pursuant to this preferred form of disclosure I I have shown the grid 10,;grid leak 2and its associated condenser 3 -*The variable 'con-' ment-battery 12 from becoming discharged,

the method and apparatus is de communication betweenmembers of the airden ser 4 and the inductance 5 form a; tuned circuit 18 the function of which will bemore' fully explained later. The tickler coil 6 is Y inductively associated with theinductan'ce 5, and isin series with the plate7, the telephone 8 (of which there may be a plurality as indicated at 8) and the source of plate potential '9, The filament 11 is; fed from the fila-- merit-battery "12. The amountpf filament current may be regulatedjby-the rheostat 13. Across the filament batteryf12 is connected a circuit 17 comprising the inductancel, the microphone transmitter 15 and tli'eswitch 16. There maybe a plurality of microphones and switches asindi'cated at 15' and 16. The, inductance 141is in inductive relation-with the inductance 5. Theswitcheslfi and 16 are closed when the intercommu'nication system is inuse. When opened theypreventthe fila 76 hencethefnormal position" of the switches 16 andlfi is open when the interconnnunicating system is not in use; Y i

The operation of my invention is as'jfollows: The switch 1 one being closed, the current fiowing in" the circuit 17 is varied in the usualmanner by the microphone 15 or 15'. Due to the inductiverelatibn between the. inductance 14 and the inductance 5, a variation of current in the former'will'induce 'anEl 80' M.1F. in the latter, which in turn will cause a corresponding variation of potential of the gridIO. B v the action of thefltubefl these variations oflgridpotentialresult inaudible signals in the telephones 8or 8' A This is the general operation of my invention,and is sufiicient to give clear and distinct communication under normal v conditions. Conditions may arise however where ,it may be nece'ssaryto greatly increase the volume of the signal in the communication systembf my invention. As an example," the noise of an aircraft motor has heretofore made infer-E was crew either impossible or ex remely unreliable. Withmy invention such 'com municati'o'n becomes reliable 1 and 'easilyfeffected," Toobtain=successfuloperation under'a'd verse conditions'of the type described I have age when the tube is not Oscillating for in the means such as varying the inductance would be suitable. By tuning the circuit 18 and by operating the tickler coil 6, the tube 1 may be caused to oscillate and the frequency of the oscillations controlled. With the tube in an oscillating condition the voltage across the condenser 4B which is impressed upon. the grid is large in magnitude compared to such voltlatter case it is onlythe voltage induced in the inductance 5 as above described.

changed by a change in the impedance of the adjacent circuit 17 the voltage impressed on the grid of-the oscillating tube 1 undergoes relatively large variations proportionate to the variations of'impedance in the circuit 17, and thus the signal to be transmitted .is' reproduced with large volumeand intensity in the telephones 8 and8". V

7 It will be understood that while the tube 1 may be a tube of the regular radio receiving set employed,the circuits of my inventionassociated with this tubemay be separated from the circuits of the receiving set associated with the same tube. Furthermore, in place of the telephones 8' and 8 there may be one or more stagesof' amplification-,and

wherever a telephonezis employed, a loud speaker may be substituted.

7 Furtherobjects of my invention'are now apparent. For instance, a-member of an air crafts crew wearing the telephones 8 and 8' may receive signals from a distant "station and yet be in instant communication with other members of the aircrafts crew. If external noises. are excessive the tube 1 may readily be put into the oscillating. state thereby makingintercommunication.' I

It will be understood. thatthe above description and accompanying drawing com prehend only thegeneral and. preferred embodiment of my invention and that-minor detail changes inthe construction and arrangement of parts may be made within the scope of. the appendedclaimswithout sacrificing any of the advantages of my invention;

The invention herein described may be manufactured and used by or for the Government of the United States for govern- 7 mental purposes without the payment tom of any royaltythereon ortherefor.

, Havingthus described my inventionwhat I claimista '7 1.- In a; combined oscillating detector radio receiving and local voice in-tercommun-icasystem, a vacuum tube having inp-u-tand output circuits", variable impedance means associated with. said input circuit,meansin saidv output circuit inductively associated with said variable impedance means whereby said vacuum tube is placed inan oscillating state,whichaforesaid elementsare-a part of the oscillating detector radio receiving system, in combination'with an impedance circuit the impedance of which may be independently varied at a predetermined point said point lying outside the physical limits of said receiving system, means whereby a variation in the impedance of said impedance "circuit will produce a variation in the impedance of: said impedance means associated wlth said lnput circuit, whereby radlo sign als may-be observed as well as local intercommunicat ion voice frequencies.

' "2; In a" combined oscillating detector radio When the impedance of the circuit 18 is.

receiving and local voice .i ntercommunication system, a'va'cuum tube having input and outputcircuits, variable impedance means associated with said input circuit, means in said output circuit inductively associated with said'variable impedance'means whereby said vacuum tube is placed in an oscillating state, which aforesaid elements are a part of the'oscillating' detector' radio receiving system, an impedance circuit the impedance of which may be independently'varied'at a plurality of independent points said points lying outside the physical limitszof saidreceiving system, means whereby a variation in the impedance of said impedance circuit will produce avariation of said impedance means associated with said input. circuit, whereby locally generated voice frequencies may be observed. in a plurality'oftelephone receivers inthe output circuitof saidreceiving system.

3. Inc combined oscillating detector rad io receiving and local voice intercommunication system a vacuum tube having grid filament and plate electrodes, variable impedance meansyassociated with said grid electrode, means associatedwith said 'plate'electrode and inductively associated with said variable impedance means whereby said tube is placed in an oscillating stateand a source of electrical energy for saidfilament electrode, which aforesaid elements constitute a partof an autodyne receiving system, in combination with '.a circuit connected across said source; of electrical energy said circuit including a coil anda'microphonasaid coil being inductively'associated with said variable impedance meanswhereby radio as well as intercommunication voice frequencies may 1 across said source of electrical energy said circuit including a coil and a plurality of microphones, said coil being inductively associated With said variable impedance means whereby radio as well as intercommunica tion voice frequencies may be observed.

5. In an intercommunication system, the combination of a vacuum tube having a gridfilament circuit consisting of a grid leak and condenser and a tuned circuit, a plurality of microphones in a circuit inductively coupled to said tuned-circuit, whereby the impedance of said tuned circuit is caused to vary according to voice frequencies impressedjupon any of said microphones; a plate-filament circuit consisting of a source of power, a plurality of telephone receivers corresponding in number to said microphones and respectivelylocated adjacent thereto and a regenerative inductance which is coupled to said tuned cir. cuit, whereby said vacuum'tube is caused to oscillate at a frequency determined by said tuned circuit and the voice frequencies impressed upon said microphones are greatly amplified and observed in said telephone receivers, in said plate-filament circuit.

6. The method of intercommunication in an area, provided with an oscillating detector radio receiving system having a radio detector input circuit for external radio reception, including the steps of varying the impedance of said circuit according to local voice frequencies and receiving on said system said radio and intercommunication voice frequencies.

7. The method of intercommunication in an area subject to external noises of greatvolume, said area being providedwith an oscillating detector radio receiving system having a radiodetector input circuit for an ternal communication, including the steps of tuning said receiving system to a fre: quency on which no radio signals are heard and varying the impedance of said detector input circuit according to local voice fre-' quencies and receiving on said system the said intercommunication voice frequencies;

8. The method of intercommunication in an airplane provided With an oscillating detector radio receiving system, having a radio detector input circuit for external communication, including the steps of energizing .a microphone circuit by the regular filament r battery associated-with said detector circuit said microphone circuit being inductively coupled to said detector input circuit, varying the impedance of said detector input cir cuit by varying the current flowing in said microphone circuit according to local voice frequencies, and receiving on said system said intercommunication voice frequencies.

FRED BENJAMIN MONAR. 

